2020-05-13_REVISION - C1981010 (41)

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A summary of the estimated mine closure cost is presented in Table 1.4-1. Please refer to Map M6 for the post mining topography for the worst case bond year(2022) and to subsequent tables and sections in Appendix A of the permit application as indicated in Table 1.4-1 for more detailed analysis and discussion. The bond amount of $29,962,241 will be applied to our permit revision (PR9). This represents the worst case cost for the period 2018-2022. Trapper estimates that during the worst case year of 2022, the total disturbance within the approved permit area will be 1,587.8 acres, which includes miscellaneous areas such as light use roads and silo locations. The increase in the bond amount is due mainly to the development of N pit, and the more expansive nature of Trapper's current mining methods regarding the combined dragline, dozer stripping, and pre-stripping by the Truck/Excavator operations. 1.4.1 Regradinq Regrading would be the initial reclamation activity conducted at a mine if the operator permanently ceased operations. The areas requiring regrade at Trapper Mine, if this improbable event occurred, would be the open pits and associated spoil piles, roadways, impoundments, and ash disposal area. Regrade costs are summarized in Appendix A, Table A-3. Supporting calculations are shown in Tables A-4.1 through A-4.5. 1.4.1.1 Pit Regradinq The pit regrading costs for Trapper Mine include the Lancaster(L), Nighthawk (N)and A Ash pit areas. Conceptually, the backfilling of the open pits would be accomplished mainly through grading of highwalls and spoils with dozers. Nighthawk pit would also include truck and loader backfilling. Lancaster pit would require some blasting and highwall reduction. The cross sections used to calculate the volumes shown for all pits in the regrade tables are included in Appendix A. The spoil diagrams that are the basis of the regrade sections were developed using Mincom software, and are a relatively accurate depiction of pit geometry before regrade. The cross sectional areas were applied to incremental pit lengths for the worst case year of 2022. The number of cross sections constructed for each pit depended upon the total pit length, and the variability of overburden and interburden depths. Dozers would do the backfilling and grading as this is the most cost efficient equipment other than draglines, given the average distances calculated. Caterpillar D10T dozers were selected as the most efficient equipment to complete the regrading task. Some truck/excavator work was required to backfill the N pit, and to insure positive drainage. Pits will generally be backfilled using spoil material currently available within existing spoil rows associated with each pit. In N pit a temporary spoil pile will be utilized for final backfill placement. Appendix A provides appropriate cross sections of existing and regraded post- mine topography. 1.4.1.2 Roadway Regradinq For purposes of estimating reclamation cost, three types of roads have been identified at Trapper Mine, which include access, haulage, and dragline walk roads. These roadways are designed and constructed to minimize amounts of cuts and fills, which minimizes the amount of backfilling and grading that would be necessary to return them to a satisfactory 1-34 Revision: 2-o Approved: